Assembly of a plant for gas separation

ABSTRACT

For assembling a plant for gas separation which comprises at least one separating column and a surrounding casing, the separating column ( 1 ) is prefabricated in a workshop and provided with pipe bridge modules. The separating column ( 1 ) is positioned horizontally on the construction site such that the pipe bridge modules ( 2   a - d ) are on the upper half of the column periphery along an axis parallel to the preferential axis of the separating column ( 1 ). Accessory parts are at least partially mounted on the pipe bridge modules ( 2   a - d ) while the separating column  1 ) is positioned horizontally. Mounting the accessory parts in a horizontal orientation require only a small amount of scaffolding is required at the level of the diameter of the separating column ( 1 ). All the operations take place virtually at ground level. At the same time as the horizontal mounting of the accessory parts on the separating column ( 1 ), the casing is fabricated in a vertical orientation to half of its height, the upper side remaining open. After the separating column ( 1 ) has been set upright and inserted in a vertical orientation into the casing from above, the assembly work is completed and the casing is closed.

This invention relates to a method of assembling a gas separation plant comprising a separation column, a casing and accessory parts, as well as any novel apparatus relating to the method.

When constructing a gas separation plant, such as, for example, a plant for low-temperature air separation, there is basically a choice between two alternatives, either prefabricating the plant as extensively as possible in a factory workshop or assembling parts of the plant only at the construction site. In the first case, given the large size of the separating columns, such plants frequently entail a high outlay on transportation. The second alternative requires considerable assembly work to be carried out in surroundings which are not particularly suited for this purpose. A major part of the assembly involves installing a separating column into a casing, for example a cold box for thermal insulation.

European patent application EP913653 describes a prior art method in which the separating column is lifted into a horizontal, upwardly open casing in the factory. The finished combination of separating column and casing is then transported to the construction site. By contrast with this method, the cited document itself discloses prefabricating only the separating column. At the construction site, the prefabricated separating column is inserted horizontally into the open casing, this casing lying on its side.

German patent application DE20316731 describes installing the separating column into a horizontal casing which is open on one side. The application in question discloses transporting the prefabricated separating column to the construction site, where it is lifted into the horizontal, upwardly open casing. Furthermore, the combination of separating column and casing here is accessible from above, which means that it is not absolutely essential for accessory parts, such as, for example, pipelines, instruments and/or valves, to be preassembled; instead, they can also be installed directly at the construction site into the casing which is open from above. The whole combination of separating column and casing is then brought by crane into its vertical end position and the casing is closed.

Both of the assembly variants described in the prior art have the disadvantage that the casing has to be constructed with very high mechanical stability while consuming an unnecessarily high quantity of material. In both assembly variants, the whole combination of separating column and casing is brought into the vertical position. The casing and its connection to the separating column must be designed to be stable enough to be able to take the total weight of the separating column during the process of setting the combination upright. This stability requirement far outweighs the stability requirements for the subsequent operation of the plant. During the operation, the casing serves for thermal insulation and has therefore only to absorb the wind loads. The unnecessarily high stability during the setting-up process means that the consumption of material for the casing is therefore considerably higher than would be required for the steady-state operation.

In addition, the different temperatures need to be taken into account when assembling and constructing such plants. The assembly is performed in a warm state (ambient temperature), whereas, in the course of gas separation during the actual operation of the plant, for example in a plant for air separation, cryogenic temperatures (60-80 K) prevail in some parts of the plant, while other parts are considerably warmer. The different temperatures which prevail result in different material expansions, these expansions having a particular effect in the case of accessory parts such as pipelines, instruments, infeeds and outfeeds and/or valves. These different temperature expansions must be taken into account during construction and assembly, specifically with regard to the positioning of the parts. This factor particularly increases the outlay for construction of parts which are accessible from outside.

A main object of the present invention is to provide apparatus and a method for assembling a plant for gas separation in such a way as to ensure a simple assembly in situ while at the same time minimizing the construction and the material costs for the casing.

Upon further study of the application, other objects and advantages of the invention will become apparent. The main object is achieved by a method of assembling a plant for gas separation comprising at least one separating column (1) and a casing which surrounds the separating column, wherein the separating column (1) has a preferential axis and various accessory parts fastened along it, such as, for example, pipes, infeeds and outfeeds, valves and/or instruments, characterized by the following steps:

-   -   a) prefabricating the separating column (1) in a workship,     -   b) attaching at least one pipe bridge module (2 a, 2 b, 2 c, 2         d) to the outer wall of the separating column, the pipe bridge         module (2 a, 2 b, 2 c, 2 d) being suitable for fastening the         accessory parts and consisting of a parallelepipedal,         cylindrical or oval-cylindrical frame,     -   c) horizontally positioning the separating column (1) on a         construction site and at least partially mounting the accessory         parts on the pipe bridge module or modules (2 a, 2 b, 2 c, 2 d)         over the upper half of the peripheral surface of the separating         column (1) while it is positioned horizontally,     -   d) at least partially prefabricating the casing in a vertical         orientation, the upper side of the casing remaining open,     -   e) setting the separating column (1) upright and introducing it         in a vertical orientation into the casing from above, and     -   f) fabricating the remainder of the casing and closing it.

A basic concept of the invention comprises transporting the prefabricated column to the construction site and at least partially carrying out the mounting of accessories, such as, for example, pipelines, infeeds and outfeeds, valves, valve seats and/or instruments at the site. These accessories are mounted according to the invention on the upper half, facing away from the ground, of the peripheral surface of the separating column. According to the invention, the accessory parts here are fastened to pipe bridge modules which are composed of a parallelepipedal, cylindrical or oval-cylindrical frame. The use according to the invention of these standardized pipe bridge modules for fastening all the accessory parts means that it is possible to predetermine the positioning of the accessory parts and considerably minimize the outlay on construction and the assembly work required in a plant for gas separation. The individual calculation of the temperature-induced longitudinal expansion is considerably simplified by the standardized fastening to the pipe bridges. The mounting of the pipe bridge modules, like the mounting of the accessory parts fastened thereto, can be performed completely or partially in the workshop or directly in situ at the construction site. In addition, mounting the accessory parts with the separating column in the horizontal position allows work to take place virtually at ground level. The separating column must only be scaffolded at the level of its diameter. The at least partial prefabrication of the casing in its vertical orientation takes place at the same time as this, the upper side of the casing remaining open. The preassembled separating column can then be set up in its vertical orientation and be lifted through the upper, open side into the casing. The remaining accessories, should they not have already been mounted, are then attached, and the casing is finished and closed.

For the purposes of the invention, an oval-cylindrical frame is to be understood as meaning a cylindrical frame with an oval base.

As a result of the vertical fabrication of the casing according to the invention, only the separating column and not the combination of separating column/casing has to be set upright. Accordingly, the stability of the casing can be tailored to the operating conditions and does not need to adapted to the mechanically demanding process of setting upright the combination of separating column/casing. In addition, the mounting of accessory parts on the pipe bridge modules when the separating column is situated horizontally requires only a small amount of movable scaffolding. Consequently, not only are savings made in terms of the material costs of the casing, but also the outlay on scaffolding for the assembly work on the construction site is minimized.

In a preferred embodiment of the invention, prior to introducing the separating column, the lateral surfaces of the casing are prefabricated to a height amounting to a third of its overall height, particularly preferably to half of its overall height.

It also proves advantageous to completely mount all the accessory parts on the pipe bridge modules on the separating column in its horizontal orientation prior to setting it upright into the vertical and introducing it into the casing, this taking place over the upper half of the peripheral surface of the horizontal separating column.

In another embodiment of the invention, pressure testing and/or quality testing on the separating column and/or X-ray testing on the weld seams are performed when the separating column is in the horizontal orientation and before it has been set upright. In the horizontal orientation, all parts which are essential and need to be tested are very readily accessible, with the result that the testing can take place with little outlay.

Preferably, a plurality of pipe bridge modules are fastened to the peripheral surface at regular intervals, particularly preferably at intervals of 6 m to 8 m, along an axis parallel to the preferential axis of the separating column. In the assembly method according to the invention, this axis is situated on the upper half of the peripheral surface when the column is positioned horizontally. The positioning of the pipe bridge modules along a single axis additionally simplifies the construction of the plant. The pipe bridge modules predetermine the position of all the accessory parts. The fastening of the pipe bridge modules along an axis allows the assembly to take place in a horizontal orientation of the separating column before it is set upright into the vertical end position.

In a preferred embodiment of the invention, the bars of the frame comprising the pipe bridge modules are made of chromium-nickel steel. It proves particularly advantageous to configure the frame as a cuboidal frame.

Advantageously, a partitioning is fastened to the pipe bridge modules, the partitioning surrounding flanged components and/or instruments which are accessible from outside the casing, and the partitioning forming a volume around the components and/or instruments that is not filled with insulating material (perlite or the like). This partitioning is any hollow body around the flange-mounted accessory parts that is suitable for forming a volume around the flange-mounted accessory parts that is not filled with an insulating material (perlite) in the intermediate space between the casing and separating column. For safety reasons, flanged connections must not be surrounded by the insulating material (perlite). To ensure external accessibility to the flange-mounted accessory parts, such as, for example, measuring instruments, these accessory parts are surrounded by the partitioning. This partitioning can in this case be advantageously fastened to the pipe bridge modules. The partitioning results in the formation of a hollow space around the flange-mounted accessory parts which simultaneously constitutes a hollow space insulation.

In order moreover to avoid convection and achieve thermal insulation for the externally accessible accessory parts, the partitioning is advantageously filled with glass wool in rigid regions, preferably of about 400 mm, behind the gas-tight access to the casing (for example a manhole).

According to a particularly preferred embodiment of the invention, the separating column is formed by an air separation column. This can be a double air separation column, for example, which comprises a high pressure column, a low-pressure column and a main condenser. The casing here constitutes the wall of a cold box whose empty spaces are filled with insulating powder or granular (perlite) before the plant is put into operation.

The present invention makes it possible in particular to simplify the assembly and construction of a plant for gas separation and to reduce the material costs for a casing of a separating column.

The invention will be explained in more detail below with reference to an exemplary embodiment described in the figure, in which:

BRIEF DESCRIPTION OF DRAWING

FIG. 1 shows a separating column with pipe bridge modules

FIG. 1 shows a separating column (1) with pipe bridge modules (2 a-2 d) which is installed in a plant for gas separation by the assembly method according to the invention. The separating column (1) is prefabricated in a workshop and provided with pipe bridge modules (2 a-d). The separating column (1) is positioned horizontally at the construction site such that the pipe bridge modules (2 a-d) are on the upper half of the column periphery along an axis parallel to the preferential axis of the separating column (1). The pipe bridge modules (2 a-d) can be attached partially or completely in the workshop or else only at the construction site. The accessory parts are mounted on the pipe bridge modules (2 a-d) at least partially while the separating column (1) is positioned horizontally.

The fact that the accessory parts are mounted in the horizontal orientation means that only a small amount of scaffolding is required at the level of the diameter of the separating column (1). All the operations take place virtually at ground level. At the same time as the horizontal mounting of the accessory parts on the separator column (1), the casing is fabricated in a vertical orientation to half of its height, the upper side remaining open. After the separator column (1) has been set upright and introduced in a vertical orientation into the casing from above, the assembly is finished and the casing is closed.

The entire disclosures of all applications, patents and publications, cited herein and of corresponding German application No. 102007029436.2, filed Jun. 26, 2007 are incorporated by reference herein.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions. 

1. A method of assembling a gas separation plant comprising at least one separating column (1) having an axis and a peripheral surface, and a casing having lateral surfaces which surrounds the separating column, wherein the separating column (1) has accessory parts comprising at least one of piping an infeed and an outfeed, a valve and instrument in said method comprising: a) prefabricating the separating column (1) in a workshop, b) attaching at least one pipe bridge module (2 a, 2 b, 2 c, 2 d) to the outer wall of the separating column, the pipe bridge module (2 a, 2 b, 2 c, 2 d) being suitable for fastening the accessory parts and comprising a parallelepipedal, cylindrical or oval-cylindrical frame, c) horizontally positioning the separating column (1) on a construction site and at least partially mounting the accessory parts on the pipe bridge module or modules (2 a, 2 b, 2 c, 2 d) over an upper half of the peripheral surface of the separating column (1) while the separating column (1) is positioned horizontally, d) at least partially prefabricating the casing in a vertical orientation, said casing having an upper side remaining open, e) setting the separating column (1) upright and introducing the separating column (1) in a vertical orientation into the casing from above, and f) fabricating the remainder of the casing and closing it.
 2. A method according to claim 1, prior to introducing the separating column (1), prefabricating the lateral surfaces of the casing to a height amounting to a third of its overall height, while leaving the top of the casing open.
 3. A method according to claim 1, wherein the accessory parts are premounted on the pipe bridge modules (2 a, 2 b, 2 c, 2 d) over the upper half of the peripheral surface of the separating column (1) when the separating column (1) is in the horizontal position (1) and before the separating column has been set vertically upright and introduced into the casing.
 4. A method according to claim 1, further comprising pressure testing and/or quality testing of the separating column (1) and/or X-ray testing of weld seams is performed when the separating column is in the horizontal orientation and before it has been set upright.
 5. A method according to claim 1, wherein a plurality of pipe bridge modules (2 a, 2 b, 2 c, 2 d) are attached to the peripheral surface of the separating column (1) at regular intervals, along an axis parallel to the axis of the separating column (1).
 6. A method according to claim 1, further comprising fastening a partition to the pipe bridge modules (2 a, 2 b, 2 c, 2 d), the partition surrounding flanged components and/or instruments which are accessible from outside the casing, and the partition forming a volume devoid of insulating filler around the components and/or instruments.
 7. A method according to claim 1, wherein the separating column (1) is formed by into an air separation column.
 8. A method according to claim 2, wherein said height amounts to half of the overall height.
 9. A method according to claim 5, wherein said regular intervals are between 6 m and 8 m. 